Electronic image processing often involves modifying images, such as photographs, to improve them in some way, while maintaining the appearance of a true record of an actual event. "Touching-up" an image is possible with photographic techniques, but such procedures may be carried out with greater ease in an electronic environment, where less special expertise is required on the part of the artist. Thus, electronic systems are available which allow a very large amount of commercial artwork to be enhanced in ways that would be far too expensive if carried out using the photographic approach.
In the enhancement of artwork, a common requirement is for undesirable features, such as man-made objects in a landscape, to be removed. Pixel data from a source portion of an image (the background) is copied to a destination portion, i.e. that occupied by the undesirable object. In a known system, operations of an artist result in the two portions being identified, whereafter the machine replaces pixel values in the destination region with values equal to those in the source region. Thus, each pixel in the destination region has a respective pixel in the source region resulting in a patch of pixels being replicated so as to reproduce the texture of the source region. However, known systems faithfully remove undesirable objects by pixel replication, but they may also introduce new artefacts where the replicated region joins the existing background. Therefore, although providing a fast means of modifying an image, care must be taken to ensure that the modification cannot actually be seen in the finished artwork.
It is an object of the present invention to provide an improved image processing apparatus of the aforesaid type.